A New Paradigm for Understanding Garment Warmth
on 02/20/2009 21:40:01 MST

Yesterday I read some BPL posts answering questions about low budget garment outfitting for ultralight backpacking. It struck me how confusing all the options must be for a newbie. I then thought that warmth relative to Polartec fleece products might be the easiest way for people to understand their options without having to wade through technical jargon or vague environmental descriptions. This post is an attempt to see if this different approach makes sense to people.

If I say, “It is the same warmth as a Polartec 300”, everyone can understand.

If I say, “The Patagonia Polarguard Delta Pullover’s intrinsic clo value is 1.06 and its total clo value is .509, the experts understand, but the laymen are confused.

If I say, “The Patagonia Polarguard Delta Pullover kept me warm at 30F around camp, the laymen think they understand but the experts know that the information is of little practical value to either the laymen or the expert. Without knowing the wind rate, the reporting persons BMR, the MET rates and durations for their camp activities, and the change in the reporting persons core temperature at the beginning and the end of the camp activities it is impossible to ascertain the insulation value of the garment they are reviewing.

I created the following chart to be Montbell centric. The other garments I listed are common alternatives to comparable Montbell garments.

Trying to determine the warmth of a garment by just measuring its loft is a measure of futility. For example, the Patagonia Polarguard Delta Pullover and a Wild Things Primaloft One sweater both have a loft of .6”. The Wild Things sweater is more than 27% warmer. The Montbell Alpine jacket has 2” of loft and box baffles yet the New Balance Fugu, which uses sewn through construction, and only has 1.5” loft is 64% warmer. The Montbell Alpine Jacket and the Montbell Permafrost Parka both use box baffles and have 2” of loft; the Permafrost Parka is 41% warmer. A Polartec 300 jacket has .25”loft and a Patagonia Polarguard Delta pullover has .6” loft and yet their insulation value is the same. The only two cases in which the loft is relevant is if you want to compare synthetic garments using the same insulation type and quilting. The other case is base layer garments; their warmth is correlated with their thickness.

In January 2010 there were a number of posts asking for clarification of the specific fabrics I tested. I answered these questions in separate forum posts. In addition, I updated my chart to includes fabric weight information. Version 2 of the chart is as follows:

In January 2011 there was a request to add information regarding how wind would affect the insulation value of each garment. I answered this related question is new post at http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=42263&skip_to_post=359270#359270

Re: A New Paradigm for Understanding Garment Warmth
on 02/20/2009 23:11:41 MST

F%$king brilliant Richard! (excuse my French)

I remember coming up against this exact problem when I started looking at lightweight clothing alternatives. You're right... for most traditional backpackers fleece is the gold-standard for comparison, and almost everyone knows how warm it is.

The funny thing is though... I recall asking you in a thread about the MB alpine light down jacket and you said it had a similar clo value to 300 weight fleece (you even made me a graph!). I remember being surprised, because my 300 weight fleece isn't that amazingly warm. But this bar graph sets it all straight! It agrees very much with my own qualitative judgements of warmth now that I know some of the garments. And, indeed, the MB light alpine jacket is *much* warmer than 300 weight fleece!

Anyway, excellent work. This is going to be very useful for newbies. Actually, it'll be useful for just about anyone! (including me!)

Hi Ashley, the Thermawrap Parka uses a heavier insulation than the jacket, a fair bit heavier in fact. The Montbell site quotes the jacket as using 50g/m2 Exceloft, while the parka is listed as 80g/m2. My understanding was that the parka used the heavier insulation through the torso while using the lighter insulation in the arms and hood, however Montbell does not infer this distinction in their specs or product description.

I have a few things to add to Paul's recommendation to purchase the Fugu including the warmth of the jacket, the fabrics used, and the looks. The New Balance Fugu claimed 4.6F increase in warmth based on the liner piqued my interest and so I did some tests. First, this is what the liner looks like magnified:

:Liner

The tricot protection layer looks identical to the third layer used to protect eVENT and Gore-Tex membranes but, I have never seen the silver membrane below it before. Has anyone seen a similar liner before or know anything about this type of liner? For example, is it microporous or hydrophilic?

The Fugu tested significantly warmer than a Cabela's down jacket with the same single layer loft of ~1.5". It is very much warmer than a comparable loft down jacket than the modest 4.6F claim in their marketing hype. I suspect that this is primarily the result of the 850 down in the Fugu versus the 650 down in the Cabela’s. None the less, this unorthodox liner probably does make the incremental 4.6F contribution New Balance claimed.

My simple test was to IR measure the heat transmitted through the jacket in a 70F room and compare that with an identical loft down jacket and a jacket previously warmth tested by BPL. I used a regulated 135F (65F delta) heat source under each jacket and let each jacket acclimate for 1 hour. The mean 95F skin heat passing through the jackets in a typical 30F (65F delta) winter environment was simulated with this simple test. One other reference jacket I tested was the MEC Magma (1.1" Primaloft One). BPL previously tested this jacket as part of their Synthetic Belay Jacket tests.

The less heat moving through the insulation and measurable on the outside surface, the better is the jacket’s insulation. To put the above numbers into another frame of reference, I tested my comparable weight Patagonia Micropuff pullover (.6" Polarguard Delta) and it yielded 90.1F of heat to the outside surface.

The material is quite windproof. A simple mouth breathability test yielded an undetectable air flow similar to the Epic Praetorian used in the Special Forces PCU Level 4 Windshirt.___________

Does your test measure conductive heat loss? You seem to have measured only IR heat loss.

Considering average loft is 70% of max or 1.05", this give the garment and incredible clo of approx. 6.18/inch... Did you take the IR test measure at the point of highest loft? Then the effective clo value would be 70% or 4.326. If not I wonder why everybody at BPL doesnt own one.

Thanks Richard! Your posts are some of the most informative on this site. This is a great tool for people picking insulation layers, too bad it can't be made a sticky post. I would love to see this updated regularly with other silmilar garments to see how they stack up.

I often talk about how much I have used and loved my Mont-Bell Thermawrap jacket (mine is a 2005 model). In the winter I often use it in conjugation with my Patagonia R1 pullover and rain coat. I guess that combo isn't as warm as I thought.

Re: A New Paradigm for Understanding Garment Warmth
on 02/21/2009 18:02:51 MST

Richard,Have you ever tested any of Under Armour's products? I am thinking specifically of their Cold Gear garments and their Compression garments. From a layman's perspective, I have been impressed, but would be very interested in your expert opinion, if you have worked with them.Thanks much,Tom

Richard thank you for the information; I for one, as a newbie UL backpacker, really appreciate it. I have a, probably very obvious, question: I own both the MB UL jkt and the Thermawrap Jkt - if I was to wear both at the same time would I just add the Iclo values, or is the value higher because of the insulation gap between both layers? Many thanks in advance,

Maybe I have just not been following this conversation, but am I the only one who is amazed at the NB Fugu beating the Permafrost, a jacket designed for cold weather climbing? Richard, how are these items tested? I would assume that the Permafrost would still be "real-world" warmer just due to the hood, but the Fugu is just amazing me given that it is 10 ounces lighter. I'm amazed- a 14 ounce jacket that is warmer than a belay parka... this is revolutionary to me.

The difference between the permafrost and the Fugu is that the Permafrost has a much heavier shell. The Permafrost has "only" got 9 ounces of fill but weighs 25 oz. So presumably it is designed to be pretty bulletproof. The Fugu, on the other hand, weighs 13-14oz I think but has a much much lighter shell... so it's possible it may have more down in there or at least a similar amount.

But yes, pretty amazing! Goes to show you that sewn-thru baffles aren't that great in comparison to having extra down.

You're right, the materials will add weight- though the Permafrost should be very warm for its weight given its welded box construction, 9 ounces of 800 fill down, and rather thin shell (15 and 30 denier). It's actually not tough enough for me, which is one reason I have stayed away from it. Still, it appears that the radiant liner of the Fugu is of greater value- warmth wise- than more down fill...

This is a fantastic graph. Suprising to me is how high powerstretch is up there, I wish it had less elastine (12%) which (I believe) makes it slower drying. It's also a bit fragile (the mountain hardware Zip top I had was anyway).

Re: A New Paradigm for Understanding Garment Warmth
on 02/22/2009 04:32:27 MST

Actually, this is a kind of graph I would like to see in the BPL wiki with regular updates to reflect current available pieces. I've started writing for a local outdoor magazine and I'm planning to write an article about insulation comparing fleece with high loft insulation. Most people overhere still buy fleece when they want something warm and I would want to introduce high loft insulation. This graph would seem like a perfect idea for comparing both without making things to complicated.

Yes, Thanks to you Richard I am now rethinking my insulation systems. It looks like the Mont-Bell UL Inner Down Jacket is really warm for it's weight. I think I need to pick up the jacket and the pants.

BTW- Does anyone know anything about the new Cocoon stuff? I would love to know the approximate clo and weight. As well as a anticipated release date.

RE: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 06:51:18 MST

Just want to add another newbie "thank you". This definitely helps me out. I’d like to think that examples like this will help me understand some of the other more technical discussions on here as well.

Huzefa, you are going to have to help me out with your chart- I have no idea how to translate that as a means to deduce the proper down fill for a specific garment.

If 9 ounces of 800 fill power down is not optimum for the Permafrost (I assume you mean it is underfilled?) then what would be the ideal amount. 9 ounces is used by Nunatak (Kobuk) and Feathered Freinds (volant) in similar jackets, and I assumed it was standard for a good belay parka.This is not academic to me- my DAS will die next season and I am switching to down.

P.S. I hope this doesn't sound combatative, but the kind of information being offered in this thread is what I would like to see formalized by BPL, and it's lack is why I let my membership lapse. I feel that I gain more information on the forums than through the articles... just some feedback for the site.

The table I posted is infact Richard's work which I copied from his old post but I forgot to mention that.

Quoting Richard again: "If you opt for 800 fill down baffles filled for optimal thermal density, they will out-perform (>oz/inch/yd2-green, >clo/in/yd2-red, >clo/oz/yd2-blue) the best synthetics when dry. If you opt for max loft only, you will have better oz/inch/yd2-green (eye candy) but you will not have a higher clo/oz which is the most critical measure for backpackers."

Permafrost has 2" loft, clo of 5.33 or 2.665/in and as you say has 9 ounces of 800+ down. You will need 2.46x time down i.e. 22.1 oz of total down to achieve its potential of 6.562 clo/in or 13.124 clo.

That would be too warm for your needs. Unfortunately no one makes garments to achieve max warmth/inch and max warmth/oz as they require radical designing which is too costly to manufacture. Also most people equate warmth to loft so its bad from business perspective.

My suggestion is to not worry about this since such products dont exist and let Richard's chart help you with your selection.

Unfortunately no one makes garments to achieve max warmth/inch and max warmth/oz as they require radical designing which is too costly to manufacture.

I would disagree somewhat. All that is required is to use smaller baffles and stuff more down into them -- so you get a density which is closer to optimum. For instance, you could shove a whole lot more down (3 times as much?) into the MB inner jacket without needing to make the baffles bigger. Then you would have a very warm jacket without needing to make a bigger, heavier shell to hold it. Easy.

Of course, Huzefa has identified the reason manufacturers don't do it... loft sells. If one jacket looks puffier than another it must be warmer right? Guess which one the average joe is going to purchase?

A New Paradigm for Understanding Garment Warmth
on 02/23/2009 16:25:27 MST

Over stuffing down garments actually produces clothing that is not as efficient warmth for weight. The optimum amount of down is that which can loft fully without being too loose. Once the down cannot loft fully there is no advantage in adding extra down.

I also think that thickness is a good general indicator of warmth. It's not the only one of course but I think it is important, despite what some are saying here. Shell fabrics, baffles and radiant barriers all play a part but thickness is key.

Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 16:48:57 MST

Over stuffing down garments actually produces clothing that is not as efficient warmth for weight. The optimum amount of down is that which can loft fully without being too loose. Once the down cannot loft fully there is no advantage in adding extra down.

I understand that this is the generally accepted view. But Richard Nilsey has some very persuasive data which shows otherwise. In particular, it appears that down can be stuffed at about 2.5x the density that it is normally done, whilst still getting full value for warmth. The idea that down needs to "loft fully" so that it spreads out as much as possible is not correct (again, according to Richard's data and some published papers). Having said this, there is a point at which adding extra down starts to produce smaller gains, and eventually you even go backwards. But there is a linear region where warmth increases proportionally to the amount of down (even if it is "overstuffed").

I don't have the links to the threads where this was all discussed, but if you have a search through Richard's posts in the past year you will find them. Have a read, it is very enlightening!

Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 16:57:54 MST

Hey Chris, in case you haven't seen them here are the threads I was referring to (well, 2 of them anyway). Here's the original thread and there are some further comments in this thread which clarify a few points.

A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:14:23 MST

I accept that down can be stuffed at more than the density used by many makers (though not all - Rab and PHD with some products for a start - PHD will add down if requested) which is why I said overstuffed. There comes a point at which the weight added by extra down isn't justified by any increase in warmth. Of course down doesn't need to spread out as much as possible. Indeed it can't unless an item is very under stuffed. By "lofting fully" I mean to the optimum amount for the maximum warmth for that amount of down.

I've used down bags that were definitely under filled, leading to cold spots as the down could shift too easily. The apparent loft before use wasn't actually there over the whole bag.

I still maintain that thickness is a good general guide to approximate warmth for those - the majority I'm suspect - who don't want to go into technical details.

A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:30:35 MST

Ashley, I've read the threads and some of it makes sense. I'm not convinced that in the real world these figures really make sense however. And I'm always interested in what happens in practice. To give two examples regarding the compression of insulation. Testing inadequate sleeping bags that didn't live up to their temperature rating (something I've done too often) I've used down jackets to boost the warmth. I've found that wearing the jacket in the bag isn't very efficient if it's a tight fit. It's far warmer to spread the jacket over the bag so it isn't compressed. Now maybe I've always had jackets with optimum density of fill - if so there's quite a few of these about as I've used a variety of jackets from different manufacturers. I've also squeezed down bags into bivvy bags a little too small for them and found that this cut the warmth despite the extra barrier of the bivvy bag. I was warmer sleeping on the bag rather than in it. Overall my experience is that allowing insulation to loft to its maximum provides the most warmth.

Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:32:03 MST

By "lofting fully" I mean to the optimum amount for the maximum warmth for that amount of down.

According to Richard's data there isn't really an optimum amount of loft for maximum warmth... rather, there is a linear region where the shell can be compressed or expanded without affecting garment (or sleeping bag) warmth.

Anyway, the interesting thing about it is that you can go a lot further than "overstuffing" a sleeping bag by 2oz. You can in fact usually double the amount of down without losing value for warmth (I think Richard have have actually tested this on a generic mummy bag).

Richard pointed out some examples at the beginning of the thread where the thickness of the garment does not correlate much at all with how warm it is. I would say that the amount of down fill (assuming same quality) is probably the best approximate and simple measure of a garment's warmth. You can't always read that on the label though.

Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:42:07 MST

I'm not convinced that in the real world these figures really make sense however. And I'm always interested in what happens in practice.

Yep, fair enough. If it's your experience that a jacket placed over a bag is warmer than in it, then you can't argue with that. Whatever works best in practice is king. There may be something else going on in those situations you describe. Perhaps the down is not compressed evenly.

It would be interesting to hear from Richard whether he has tested it on a real sleeping bag. Here's some data he posted in one of those threads, but I'm not sure where he got it from. Note the clo/kg of down doesn't change as you increase the fill:

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:50:50 MST

"If it's your experience that a jacket placed over a bag is warmer than in it"

One factor is that the jacket will be compressed underneath you when worn, not when placed over you. But this might not be significant, and perhaps countering this is that I find it hard to get all of a jacket usefully covering me without wearing it.

And of course it's not a factor in a too-tight bivy bag situation, where Chris still observed the lesser-compressed bag being warmer.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:52:12 MST

>I would say that the amount of down fill (assuming same quality) is probably the best approximate and simple measure of a garment's warmth.

I thought this was a generally accepted principle of insulation design. The more fill=the heavier insulation=warmer bag. But all most of us need to know is what is the (accurate) warmth rating of the bag compared to it's weight? I choose WM bags because, *underfilled* or not, I find their comfort rating to be accurate and their bags to be light.

A New Paradigm for Understanding Garment Warmth
on 02/23/2009 17:56:26 MST

Of course the problem with real world experiences is that there's always something else going on! Any anecdotal statement is always missing some factors. However it is in the real world that bags and jackets are used to keep warm.

Those figures are interesting. I'd like to know where they came from. 12oz is a significant amount of down.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/23/2009 23:52:25 MST

Bob (Dennis-Your question is incorporated in the last paragraph)

I have been up in the Sierras for a few days and am now just getting an opportunity to start responding to questions. First I want to say I was very impressed with your responses to Will's article on "Salomon Tundra Mid WP Insulated Boot Review". Your posts were courteous, well structured, and compelling in the support of your position... great job.

You said, "Can you tell us more about what makes for a better rating"? The fleece and synthetic insulation vendor's clo/oz ratings closely correlated with their relative performance vis-à-vis one another. The down insulation results closely correlated with the down fill amount. All insulations do a good job of blocking convection. Blocking radiation losses is the biggest variable between the synthetic insulation types and as well as the impact of down density. Based on my tests, fleece and synthetic specifications appear to be based on the inclusion of a still air layer on the outside of the insulation in addition to the insulation itself. When layering garments, frequently this still air layer won’t be present and the ensembles won’t be as warm as you would anticipate. Sizing of each layer to have at least a 6mm gap between them is necessary to approach the insulation vendor’s published clo/oz values.

You said, “When a manufacturer comes out with a "new and improved" version next year, how do we know whether or not it still occupies the same place in your table? And if not, then where it belongs?” The situation with garments and sleeping bags in the US is the same as it was with sleeping bags in Europe prior to the EN 13537 standard. In other words the consumers aren’t provided adequate information to make an intelligent decision. I suggest buying from vendors who have a reputation for honest representation of their products specifications and then try and find the closest match to something which has already been independently tested by multiple sources. It is in the interest of most manufactures and their advertising partners to use FUD (fear, uncertainty, and doubt) to discredit the value of independent testing. The only manufacturers who would benefit from having independent tests published are the one who products test best.

You said, “How do I determine where a garment not in your table fits in?” You can extrapolate from the existing test results. For example, in a post subsequent to yours, Dennis Park asked, “By any chance, would you know where Mountain Hardware's Compressor men's jacket would fit on your chart? Oops, forgot to mention 2007 model.” The 2007 Compressor specs were size medium [Weight] 16 oz [Shell] Superlight 15D, [Insulation] PrimaLoft One 115 g/m2. That is the same insulation type and a similar amount to what was used in the WT PL1 hoody that I tested. The Wild Things Primaloft One hoody used 2 layers of 60 g/m2. This jacket would theoretically test out with an intrinsic clo of approximately ~1.46. In other words, it is ~1.5 times warmer than a Polartec 300 weight or a Patagonia Micropuff pullover or jacket.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 00:01:11 MST

Ashley,

Thank you for the kind words. I guess that the first time I looked at the question of 300 weight fleece versus the Montbell Light Alpine question; I interpreted vendor specs to arrive at a conclusion... sorry if I screwed up the first time. This time around I actually tested each of the products myself.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 00:16:50 MST

Huzefa,

I used a guarded heat plate. It measures the cumulative heat conductivity from all modes of transmission (conduction, convection, and radiation). The measurement technique integrates the measurements in the seam, along the ramp up/down, and max loft area.

The average clo was 6.18 divided by 1.5 inches for a less remarkable value of 4.12 per inch. A stack of cotton cloth yields 4 clo per inch and so the warmth is less of an anomaly than is the clo/oz.

The Fugu failed in the market place and is no longer available. I don't think people appreciated the jacket's extraordinary value proposition because New Balance wasn't a known performance jacket vendor in the UL community.

Here is a quote from an old post of yours -"The Fugu down jacket is 800 fill and the Cabelas down jacket is 650 fill. They are sewn through construction. 1 1/2" is the maximum loft. The baffles average 5" wide. Only approximately 2" of the 5" is at the maximum loft. 1 1/2" on either side it ramps up from a few mm to 1 1/2". My crude estimate is that the average loft is about 70% of the max or 1.05"

Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 01:37:06 MST

I've always wondered why people don't also consider the heat sink effect of different materials in clothing. In buildings the R-value of a material can affect the temperature sensation of a room; even though the air in the room may be the same temperature, the materials used in the walls and the floor, when touched, can make the room feel cold or hot. That's why, on a cold day, rooms with wooden walls and floors tend to feel warmer than rooms with stone walls and floors. Some of the jackets that I have when I touch the outer nylon fabric feel much colder to the touch than others. There must be some effect of this heat sink sensation on the outer fabric, contributing to the overall feel of the warmth of the jackets.

"...We have specific thermal data on each Polartec® Thermal Pro® fabric but without knowing which Polartec® Thermal Pro® fabric you are considering, it is impossible to rate it against Polartec® Classic 200 or Polartec® Classic 300. Each Polartec® Thermal Pro® fabric is developed to meet the expected functions needed for a specific use."

I think the clearest answer is that they specify both Polartec 300 and Polartec Pro at .16 clo/oz/yd2. Polartec 300 is 10.9 oz/yd2. Common Thermal Pro fabric options are 6.9 oz/yd2, 7.1 oz/yd2, and 9.4 oz/yd2. To compare their loftiest Thermal Pro version to Polartec 300 multiply both fabric clo/oz by .16. Comparing the ratio yields 14% less warmth for the thickest version of Polartec Pro. It is a much loftier and compressible fabric and so it LOOKS MUCH WARMER and compresses much better for stuffing in a back pack. I haven’t tested any Thermal Pro garments and so this is theory only.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 10:04:54 MST

Tom,

I haven't tested the insulation of Under Amour’s products because they fall primarily into the category of base layers and it is very difficult to get an accurate measurement of insulation that thin. Base layer insulation tends to be of less importance than that of most clothing items, its tactile properties, and the way in which it handles moisture, are of much greater concern since it is in direct contact with the skin.

It is really difficult to get an accurate measurement of base layer insulation based on standards procedures. The usual American Society of Testing Materials (ASTM) method for thickness measurement requires compressing the material by 0.7 g/cm2 (.01 psi). This very mild level of compression is still sufficient to compress the fibrils at the surface of the material and these, although very compressible, do contribute to trapping additional surface air film thickness. If one uses a method where thickness is measured without any compression the measured intrinsic insulation will approximate the insulation predicted using 1.57 clo per centimeter (4 clo per inch).

The insulation of base layers is seldom a major consideration in thermal comfort, since it lies within an already trapped still-air layer between the skin and the outerwear. Indeed, static copper manikin measurements of a clothing system frequently give the same insulation measurement with or without a base layer. Nevertheless, a thicker base layer will contribute warmth in the presence of wind or body motion, particularly if the outerwear is not totally windproof, the closures are not tight, or the clothing is compressed by the weight of outer clothing layers or back pack.

A base layer’s insulation over the torso will generally be close to that approximated from its full uncompressed thickness. This is because of the air gaps between the underwear and the clothing worn over the torso. However, the insulation over the arms and the legs will be closer to that suggested by the compressed (ASTM) thickness measurement as a result of the closer fit of the outer garments.

The garment's torso is tested with a guarded hot plate to ascertain its insulation value. I tested a Patagonia down Sweater vest and determined its intrinsic clo was ~2.31. I also tested a Patagonia down Sweater Pullover hoody and determined its intrinsic clo was ~2.31. The insulation, fabric, and construction although slightly different between the garment types, yielded the same ~intrinsic insulation value. Total clo, for each garment, is determined by multiplying the intrinsic clo by the body surface area that it covers. The average body surface areas (BSA) covered by different garment types are as follows:

If you want to compare the total clo between two dissimilar garment types (for example the Fugu jacket and the Permafrost Parka), multiply the intrinsic clo value times the BSA for each garment to determine how they compare. The Fugu total clo is .48 * 6.18 = 2.97. The Permafrost total clo is .55 * 5.24 = 2.90. The hood on the Permafrost is huge but a down balaclava, in combination with the Fugu would easily beat it for greater warmth at less weight, save the relative durability issue.

My objective for this thread was to provide a very simple way to understand the relative warmth of different types of garment’s insulation. It was not to provide the total clo value for each different garment type and insulation type. None the less, for any body so interested, the above BSA values allow you to calculate ~total clo.

Thanks for the kind words. The Power Dry and Power Stretch garments are hybrid base layers/insulation layers. They need the stretch fibers to facilitate the base layer functionality only. For use on trips like Erin and Hig's coastal hiking/packrafting adventure the material gets good reviews. It is probably too heavy and warm for most UL backpacking applications.

I haven't tested the insulation of Under Amour’s products because they fall primarily into the category of base layers and it is very difficult to get an accurate measurement of insulation that thin."

Richard,Many thanks for the information. I am in the process of trying to further reduce the the clothing component of my base weight, and you have likely saved me considerable time and expense. Your insights are always appreciated.Best regards,Tom

Re: Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 12:19:17 MST

Tom and Huzefa,

Please post a link to your article after it is published. Particularly in the realm of WPB fabrics you have provided many well researched posts. I have no doubt that your article will be of similar quality.

Comparing options without making things too complicated was indeed the objective of the graph and this thread.

Huzefa - In line with those objectives, I hope that you understand that old forum posts that went into a much higher level of technical detail won't be discussed by me in this thread.

Thanks for the kind words. I have been contacted by a forum member in the Bay Area. He will provide a WM jacket and vest. I will add this info. If someone in the Bay area has a Nunatak Skaha to loan for a test, I will also add that info.

Richard,That would be much appreciated by the proud owner of a WM Ultralight with 2 oz of overfill. I think it probably was a good idea, but this question has gnawed away at me off and on over the years. I haven't had it out on trips over 11 days and those were in the Sierra in late Sept-Oct, where it worked fine. Winter trips are another question entirely and the results might well be different if I miscalculated the tradeoff.

Re: A New Paradigm for Understanding Garment Warmth
on 02/24/2009 12:50:05 MST

Chris,

I appreciate your experience based contributions to this topic. I suspect we have more common ground in our insulation views than our respective posts might lead others to believe. The same insulation types and similar densities will indeed thickness correlate with the warmth of garment. It is the exceptions in down density, down fill power, or differences in synthetic insulation types where anomalies occur. I am sure that there are one or more people in the forum audience who will peer-review at least some of the anomalies I pointed out. As these additional peer-review tests are published, we will both gain additional insights that will allow us to achieve more common ground.

A New Paradigm for Understanding Garment Warmth
on 02/24/2009 13:12:56 MST

Richard, I'm sure we have much in common and I appreciate your posts and information. I am trying to correlate your information with my experience. The down density issue particularly interests me as I have not come across this before.

With regard to down fill power and synthetic insulation I have come across many anomalies, especially with the latter. And not just between different synthetics but between apparently identical bags with identical insulation. Synthetics are not uniform. Overall I've found synthetic bags - and I've tested dozens over the years - to be over-rated, some scandalously so. I'm a warm sleeper but have yet to find a synthetic bag that keeps me warm at the claimed temperature rating. With many down bags I am warm below the lower temperature rating. I have raised this with synthetic bag makes occasionally - replies I've been given include "we know serious users don't use synthetics so the temperature ratings are just to make the bag sound good", "we know the bag isn't warm at the claimed temperature rating but our competitors claim the same for similar bags so we can't change it" and "we have no idea what the actual rating is - we just copied what other companies said about similar bags".

Re: A New Paradigm for Understanding Garment Warmth
on 03/03/2009 06:14:29 MST

Richard,

Thanks once again for this superlative post that will lead us to many excellent purchases for our gear closets and to the "gear swap" forum to make room for those purchases :-)

I think you covered some of this in your response concerning Under Armor base layers but I'll ask anyway. I use merino wool base layers but, I have some very heavy 320 and 390 weight for winter use. They feel very warm and cozy to me, but I suspect, some of that is due to the other properties (wicking, etc) that you mentioned concerning base layers in general.

My question is, at these stout thicknesses of wool, can you determine their insulation properties, as I have been wearing them as insulation, not as a base layer, although I think they function as both?

Even though these wool garments are heavy, I have preferred them for hiking over my Micropuff or my Montbell Alpine Down as I don't view these as durable enough with their thin shells, or synthetic insulation crushed by the pack, or down absorbing all my sweat. I have limited these "puffy" garments to rest stops and camp or to augment my sleeping bag. But, should these wool garments show that they don't really insulate well, maybe I should reconsider my choices.

Re: Re: A New Paradigm for Understanding Garment Warmth
on 03/03/2009 07:39:45 MST

Michael,

In summary, don’t change a thing.

The heavier Merino wool base layers, as well as the Polartec Power Dry and Power Stretch fabrics, serve a hybrid role. They address the base layer function plus adding insulation beyond what is required for a base layer. The complex weaves and bi-component nature of the aforementioned Polartec products make simple estimations difficult. On the other hand, the thicker Merino wool base layer’s insulation value can be accurately estimated. Measure the uncompressed thickness in inches and then multiply this value by “4 clo/inch” to determine where they are positioned in the insulation graph.

If you are thermo neutral (not uncomfortably cold or sweating) when hiking in your heavier Merino wool garments that is an excellent combo base layer/insulation solution. When you are hiking, you will be typically average in the range of 7 METS. You will only require additional dedicated insulation when your MET level drops significantly. While hiking, you will subconsciously vary your pace in an attempt to stay thermal neutral (not cold or hot). For the same effective temperature that you were comfortable hiking, you will require ~7/1.5=4.7x more insulation when doing camp chores. That activity is typically the province of the dedicated insulation garments.

As for your Montbell figures,i am a little confused by a former post published by you Nov 28th 2008 (not so long ago)from which i deduce that the MB Alpine jacket CLo would be around 2-2.2 , ie quite lower that what is shown in your nice graph. pls see below

François

own a Mountain Hardware Sub Zero with sewn through construction. It weighs 27 oz in size medium. This is primarily because the external fabric is 55 denier, the liner is 30 denier, and the insulation is 650 fill down. Mountain Hardware doesn’t publish the down fill weight or the clo value of the jacket. Also there is no other independent source that has published the clo value for this jacket. I tested it in my lab and it yielded an intrinsic clo value of 4.477. To put that number in perspective it is more than double the warmth of the Mont-bell Alpine jacket which is Mont-bell’s warmest light weight down jacket. The MB Alpine was also tested by me. The MB Alpine uses 800 fill and box baffles. The MH Sub Zero is an excellent jacket if you require that level of warmth in combination with extreme durability. Equivalent warmth in a jacket using 800+ fill down and lighter fabrics will require ~ 9 oz of 800+ fill

The most recent chart I published showed the intrinsic clo for the MB Alpine jacket to be 3.769. The Mountain Hardware Sub Zero tested in the same battery of tests yielded and intrinsic clo of 4.521 versus 4.477 in the earlier November test. This makes the Mountain Hardware Sub Zero approximately 20% warmer than the MB Alpine not 200% warmer as was stated in my November 28, 2008 post. I made a mistake in the November post. Thank you for a great job of consistency checking. I have now corrected the November 28, 2008 post to reflect the correct warmth relationship.

The updated November 28, 2008 post is located at http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=16819

To recap, my laboratory tests showed that the MH Sub Zero jacket with 9.2 oz of 650 fill down was approximately 20% warmer than the MB Alpine jacket with 6 oz of 800 fill down.

The down, normally allocated to a hood, is in proportion to the average body surface area increase. A jacket covers approximately 48% of your body surface. A hood covers approximately 7% of your body surface area. 7/48 = 15% anticipated increase in the amount of uniform coverage down oz by adding a hood. The fill values you quoted are approximately 28% higher for the MH Sub Zero hooded jacket. This infers that additional insulation was also added to the jacket. In other words, 300.15g of down, not 364g is required to add a hood with equal warmth to the rest of the jacket.

The MH Phantom uses approximately 9 oz of 800 fill and so it will be warmer than the MH Sub Zero jacket using 261 g (9.2 oz) of 650 fill.

200g Primaloft One insulation equals 6 oz/yd2 and 1” of loft. The theoretical clo value, based on the insulation manufacturer’s spec would be 5.040 clo. The laboratory tests I conducted on two different manufactures garments, using this insulation, yielded about 2.52 clo. By contrast, the MH Sub Zero tested 4.521.

Your reading about people using 200g Primaloft One jackets in 0F weather means nothing unless you at least know there average MET rate for the rating period in addition to the their core temperatures before and after the rating period. For example this winter I spent a full day out in -30F wind chill temps wearing only a Power Stretch hoody and hooded wind shirt and was comfortable. Although the preceding sentence is true it is of no value to your ability to gauge the warmth of a Power Stretch hoody. Only if you knew I was that my average MET rate for the day was 7 could you approximate the relative warmth of what I was wearing.

I am not sure there is much advantage in laminating Sport. Sport has minimal quilting requirement so seam stabilization may be sufficient depending on the pattern. Seam will be there even in a garment made of laminated sport. Difference in warmth will be minimal.

Lamination is done to liner.. so waterproofness will depend on shell fabric, zippers and whether it is seam sealed.

Longevity? not sure. synthetic insulation do not have much of a life anyways.

Not to belabor this point, but I also thank you for giving of your time and knowledge to help fellow backpackers understand these issues. You have taught so many of us not just the what (garment X is *relatively* warmer than garment Y), but the why (clo values, MET for different activities, BSA coverages). I think your posts let people understand this stuff at whatever level they want to or are able to. One can take away an understanding of how to calculate some of these values oneself given the right information, or simply look at one of your easily understood graphics for a quick comparison. Also fully explaining the right and wrong of long held axioms (such as loft vs down density) has changed completely how I look at some choices.

I also wanted to let you know that if you have not done any testing on the BPL Cocoon 60 jackets I would be happy to ship mine to you, and pay for return postage. Might be best to wait until June when I won't be using it. Let me know if you are interested.

Nice table, Richard. I appreciate your putting that together. Is there any chance that you could add the weight of each jacket in the table, say, in parentheses after the jacket name? That'd help make the tradeoffs even clearer.

The WT jacket in the chart is comprised of 2 layers of 60 g/m2 PL1. Other PL1 jacket's clo value can be estimated by simple extrapolation. The Pat Nano Puff uses 1 60 g/m2 layer and so it would test with approximately 1/2 the iclo value.

The Cocoon used 1.8 oz/yd2 Polargaurd Delta and the Patagonia Micropuff used 2.7 oz/yd Polargaurd Delta. Again a simple extrapolation can be used to estimate the Cocoon's iclo value from what I published for the Micropuff.

This does not seem to add up with my field observations. I own both the Ex Light and Down Inner. Subjectively, the Ex Light seems noticeably warmer to me. Does the above figure take into account the difference between 800 and 900 fill down? One factor that may make a fairly sifnificant difference is the lack of pockets in the Ex Light, which translates to less convective heat loss. On paper, I would not expect to notice any difference between the two garments, so this is puzzling to me. An additional anomoly of note is that both my Ex Light Vest and Jacket are approximately 10% below specs on weight (Size L and M, respectively).

@Chris - from an earlier post in the thread by Richard, regarding the Patagonia Down Sweater vest and Hooded Pullover: "intrinsic clo was ~2.31."

Yes, the UL Inner parka and the jacket, but I am mostly comparing the Ex Light to the current version of the UL Inner Parka, which I recently parted with in favor of the Ex Light combined with a Black Rock Beanie.

The Montbell tests (2010 catalog) list the UL and EX garments as the same Iclo. Only a .16 Iclo difference is effectively equal when you consider the tolerances between individual garments of the same type.

Richard ….I seem to have remembered that you were going to measure the IcIo of a Skaha Sweater some time back.

QUESTIONS:1.) Have you posted those measurements on another thread or just have not updated your RN Laboratory Measured IcIo graph?

2.) If you haven’t as of yet made those measurements, would I be correct in saying, that a Skaha Sweater would have a 2.7+ IcIo value with a down content (4.5oz/850+ down), compared to the MB Alpine Light Jacket (4.0oz/800+ down) of 2.51 IcIo and MB Alpine Light Jacket’s replacement, the MB Frost Line Parka (6.7oz/800 down) of 3.77 IcIo?

3.) Would I also be correct in saying, that a Skaha Sweater IcIo value with a down content (6.5oz/850+ down) would be comparable to that of MB Permafrost Down Parka (6.9oz/800 down, of about 5.25 IcIo without the actual testing of either the Skaha Sweater and MB Permafrost Down Parka?

richard, your work has added new meaning to how i look at the insulative quality of clothing. thank you for your work.

as recommended, i have tried to extrapolate from information provided. the wild things hoody has 2 layers of 1.8 oz primaloft for a Iclo of 1.46. the wild things belay jacket has 6 oz primaloft insulation. would that give the belay jacket an Iclo (based on the chart) of 2.43, which would compare to a patagonia down pull-over? having worn the patagonia pull-over, montbell alpine light and the wt belay jacket, i thought the belay was considerably warmer than the other two. is there an error in my thinking? do i need to make adjustments for the diference in shell material?

The relative warmth between garment types within the same family (down or synthetic) can be easily approximated. This assumes the typical case where the garments all use the same fabric and insulation areal weights (for example 100g/m2 PL1 and 15 denier ballistic nylon). The average body surface area for a parka is 52%, a jacket is 48%, and a vest is 36%. A vest will keep you 75% as warm as the comparable jacket, because 36 /48 = 75%, and compared to the parka it will keep you 69% as warm. A vest is generally the most efficient insulating item you can add to your clothing. To illustrate this BSA phenomenon, as discussed above, the Montbell Thermawrap synthetic vest provides 75% of the total insulation that the jacket provides yet, the ratio of garment weights is only 63%. This phenomenon holds for all insulation types.

It will be probably be spring 2011, at the earliest, before I do anymore new in depth garment testing. It is a very time consuming process and I have some higher priorities that I need to take care of first. Extrapolating from past tests is easy and so I can address your questions 2 and 3 now.2) Answer - The standard fill amount Nunatak Skaha sweater, with 850 down, has a theoretical Iclo value of 3.02 versus the MB Alpine Light Down Jacket’s 2.70 Iclo, and the MB Frostline’s 4.10 Iclo.

3) Answer – 4.08 is the theoretical Iclo for a Skaha sweater with 6.5 oz of 850 fill versus the Montbell Permafrost at 5.29.

The above estimates are predicated on proprietary regressions derived from the large battery of lab tests that I did last year.

Your extrapolation methodoly is correct. I can understand that it is hard to believe.

I found a troubling anomaly relative to every synthetic garment I tested last year; they provided consistently less Iclo than the insulation manufacturer’s specification. See http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=31482&skip_to_post=268989#268989

To give the synthetic insulation vendor’s the benefit of the doubt, I use the vendor’s insulation specification when estimating the Iclo value of a garment that I haven’t lab tested. Using this optimistic (blind faith) approach, the Iclo value for the Wild Things Belay Jacket (2009 version) is 4.96 and the 2010 version is 4.44. This would jive with your real world experience that it is considerably warmer than a Patagonia down pull-over.

Please place both your WT Belay jacket and your Patagonia down pull-over on your living room floor and place an ice cube under each. After the first ice cube melts, please let us know which jacket it was under and if the melt times were significantly different.

one useful attribute of a vest i find in winter is that it gets less moisture ...

now you might say "eric youre an effing idiot for getting down wet"

but in winter when youre playing around in the snow youll notice that your gloves, sleeves, and other peripheral areas get quite moist ... when you put on yr jacket those areas have a tendency to soak up some of that moisture as well ... DWR or not

I'm thinking a syn vest + R1 for 3 season "wet trips" (we're contemplating some trips to the PNW), thinking syn vest w/ R1 w/ a medium-ish down jacket for winter- I think a syn vest would fit into my hunting clothing scheme as well

for the Rockies, I really can't see anything replacing my ex light for three season use

I just got a new MB Ex Light jacket. I have an older 2005/2006 725 fill UL Inner jacket. I haven't worn the new one yet but was looking for comments regarding the relative warmth of one to the other. The EX is 3 oz lighter in XL but it is hard to believe it could be as warm or warmer than the UL Inner. I have worn the inner on some cold nights and stayed warm. It would be particularly helpful to hear from someone who has owned both ( the older UL Inner and the new 900 fill EX Light) Thanks in advance.

I never owned the UL Inner (but do have the Exlight)- you want to look at fill weight vs overall weight- most of the savings in overall weight are construction (no pockets, etc ) and material 7d vs 15d

then it comes "down" :) to 900 vs 725- there is a formula floating around that shows how much impact the quality of down makes

I have heard from folks that have had both, they thought the Exlight was as warm (some thought even warmer) than the UL- maybe one of them will pipe in

I have them both, and thought that the EX Light was warmer, thanks to the 900 fill down. I had serious problems with the EX Light's zipper (it eventually broke and I had to replace the jacket) and fabric, which was a long way from being down proof. I should say that my EX Light was one of the earliest on the market, and I understand that newer models have been more reliable. My Down Inner is the parka, which has a hood, a feature I really like. If buying today I'd probably go with the Down Inner.

Re: A New Paradigm for Understanding Garment Warmth
on 01/26/2011 21:14:04 MST

ahhhh .. all this timei thought polarstretch was toastier than polartech 100. now we know.a long time, and we are talk'n about 3 decades ago, Fletcher wrote at length about warmness., and to some extent this included a bit about poofyness (my word), and how some insulations feel warmer (and ARE) because they not only insulate, but poof up to exclude cold air from entering into where You are.this to me is the major reason those down jackets made of so-very-light material seem so toasty.poofy pushes out the cold. what remains is heat. (that's right.. isn't it ?)

Hi y'all ... I'm new to the site but I've been reading posts for the past month - very informative!I was wondering if I could get some advice - I'm looking for a down jacket w/ at least 800 fill power (preferably 850) & w/ a high fill weight (6.5 - 8 oz). I'm not extremely concerned w/ every little oz. of the total weight but it definitely has to bundle up very tightly when in my pack & be somewhat light.The NB fugu seems ideal but its not available in my size - I'm considering the rab infinity - it is light w/ 7.4 oz of 850 down & is actually 50g less than the advertised 510ish grams (hope that doesn't mean 50g less of down).

Based on the criteria you specified, the Rab Infinity is the fourth most suitable. The three jackets ahead of it, in rank order, are Feathered Friends Helios, PHD Yukon, and the Sir Joseph Koteka. The fifth most suitable is the least expensive and is the CAMP ED Jacket.

Thank you Richard!I think I've narrowed it down to the helios, yukon & infinity. PHD doesn't advertise its fill weight although it is 900 fill power. Would you be able to estimate its fill weight & those 3 jackets' clo values? I'm wondering whether the numerous cold spots on the infinity will substantially reduce its warmth (although will be excellent for protecting the down from shifting). The infinity also seems to be able to pack the smallest but I could be completely wrong on that.Thanks again =)

The average person can only detect a variance in a jacket's insulation in increments of .5 clo and so all of the aforementioned jackets will feel the same to you, assuming a good fit.

The secret to maximizing the efficiency of sewn through baffle garments, such as the Infinity or Helios, is to size either your wind shirt or hard shell to wear over it. The v shaped spaces between the baffle seams and the outer material of a wind shirt or hard shell create insulating air gaps that offset the loss of insulation at the seam.

The rank order I provided in my prior post was based on the ratio between warmth and weight / volume.

I'm french so sorry for my english... I was reading your messages, and I was wondering about the clo for Rab jackets such as : Photon Jacket, Generator Jacket, Xenon Jacket and Generator Alpine Jacket.

Do you have an idea ? I tried to calculate it, but the result is not correct.

Both the Microlight jacket and vest have an Iclo of 2.22. The Iclo values are to compare garments in the same class. Since the vest class only covers 75% of your body surface area, it will only be 75% as warm as the jacket class with the same insulation per unit area.

Do you know a way to calculate approximately the "temperature of comfort" or the "limit temperature" of the jackets (as for sleeping bags). The only one way to calculate de "temperature of comfort" is with : T=31-0,155 P * R with T in °C, P in W/m² and R in clo, can I say : "The jacket can help me to be confortable up to :"

Or should I say : with a micro-fleece of 200g/m² (weight=275g size L, clo=0,76 ?) and a merinos wool long-sleeves of 210g/m²(weight 260g size L, clo=0,16 ???), I have CLO = clo_jacket + clo_fleece + clo_merinos

Hi Richard,You give Rab Generator Jacket a value comparable to that of Montbell Alpine Light. The latter is much loftier (I think, at least twice) and, in my limited experience, feels warmer. What is the reason they have comparable Iclo?

It appears, from my experience and from winnowing the information from several posts, that garment loft is a relative issue, even using the same type of insulator.

Two identically constructed jackets filled with down TO THE SAME LOFT THICKNESS, one having 850 cu. in./oz. of down and the other having 650 cu. in./oz. of down will insulate differently in actual on-trail use with a pack.

The pack harness and back pad will compress the wonderfully light 850 fill down more than the "lesser" 650 fill down. Everybody knows about how well high count fill down compresses. That's great for packing it in a stuffsack, not so great when wearing under heavier or more restrictive shells and especially under a pack. You lose more insulation with the "higher cu. in./oz." down with the same compression/sq. in. compared with "lesser" down.

So maybe we need to re-think what fill weight is most satisfactory if a down garment is to be worn with a pack.

I am unsure if this information exists anywhere. Forgive me if I have missed it.

What is the relative clo value of a vest of comparable loft, down and shell fabrics compared to a jacket?

I know there may not be a simple answer. However, how much warmth are we getting, scientifically, from our down vests?

FWIW, I'm thinking of my WM Flight Vest in particular. It looks like it's a sleeveless version of their Flight Jacket. Comparable insulation value over the core, but with gaping holes where the sleeves should be.

Stephen I am not sure if this is what you are looking for but from earlier in this thread

Richard says"The relative warmth between garment types within the same family (down or synthetic) can be easily approximated. This assumes the typical case where the garments all use the same fabric and insulation areal weights (for example 100g/m2 PL1 and 15 denier ballistic nylon). The average body surface area for a parka is 52%, a jacket is 48%, and a vest is 36%. A vest will keep you 75% as warm as the comparable jacket, because 36 /48 = 75%, and compared to the parka it will keep you 69% as warm. A vest is generally the most efficient insulating item you can add to your clothing. To illustrate this BSA phenomenon, as discussed above, the Montbell Thermawrap synthetic vest provides 75% of the total insulation that the jacket provides yet, the ratio of garment weights is only 63%. This phenomenon holds for all insulation types."

also

"The garment's torso is tested with a guarded hot plate to ascertain its insulation value. I tested a Patagonia down Sweater vest and determined its intrinsic clo was ~2.31. I also tested a Patagonia down Sweater Pullover hoody and determined its intrinsic clo was ~2.31. The insulation, fabric, and construction although slightly different between the garment types, yielded the same ~intrinsic insulation value. Total clo, for each garment, is determined by multiplying the intrinsic clo by the body surface area that it covers. The average body surface areas (BSA) covered by different garment types are as follows:

If you want to compare the total clo between two dissimilar garment types (for example the Fugu jacket and the Permafrost Parka), multiply the intrinsic clo value times the BSA for each garment to determine how they compare. The Fugu total clo is .48 * 6.18 = 2.97. The Permafrost total clo is .55 * 5.24 = 2.90. The hood on the Permafrost is huge but a down balaclava, in combination with the Fugu would easily beat it for greater warmth at less weight, save the relative durability issue."

The Rab Generator uses PL1 insulation and the Montbell Alpine Light uses 800 fill power down. Loft is only a rough comparator if the two jackets have the same insulation type, the same density, and comparable fit.

If the Rab Generator Jacket feels warmer to you, my only guess is that this garment fits you better at the openings. If you have gaps at the neck, wrists, or torso then the chimney effect will purge the warm air from a garment.

Richard,No, Montbell Alpine Light feels warmer to me than Rab Generator, and the difference seemed to be more than than the difference in figures. Though, now I am confused. I will try to compare them again :)

Doesn't the fact that only the bodys core is temperature regulated to 37 degrees C mean that bodywarmers(vests) are more weight efficient, because there will be a bigger difference between ambient and body temperatures, hence vest insulation here has a greater effect.

Presumably, hats have a similarly 'boosted' effect, as I dont think you can cut blood supply to your brain when cold.

All body surface areas are not equal in importance.
on 02/18/2011 19:03:06 MST

"All body surface area is not equal

Head is more important than torso than arms and legs

If you're cold, reduced blood flow to arms and legs will cool them off, so there will be less heat leaking out there"

I have been thinking about this thread a lot while training in the cold rain these past days.I have to agree with the above statement. Even though the head has a relativeley small BSA it is responsible for a very much greater amount of heat loss due to the blood flow very near the surface of the skin.When it comes to being comfortable I and quite a few of my friends(judging by the insulating garments they wear) have found that keeping the Torso, Head, Hands ,Feet, arms, and legs warm in that order of importance to yield the best results.If someone locked me in a meat locker naked and offered me one piece of clothing at a time I might chose differently say: Torso,feet,head,hands,arms,legs due to percieved immediate comfort. Either way the head is very much more important to preserving heat than it's 4% BSA would indicate.

I have to add though that i am tentatively on board with the CLO ratings VS simple measures of loft in regards to warmth.I recently added an MLD spirit quilt with APEX insulation to my gear and have been testing it alongside my WM ulta-light down bag.The 1.75" of measured loft of my APEX is as warm as the 2.5" measured of Goose down loft. I used them both as a quilt at temperatures from 38 degrees to the low 50's. At least in my subjective determination they are equally as warm.The other factor is the momentum fabric of the MLD quilt has greater warmth to the touch. It even seems to warm up quicker but this could be due to the lack of quilting that allows less dead airspace than my down bag. I was about as stubborn a "loft is warmth" guy as there ever was but lately my experience with APEX is changing my mind.

I'm sitting here with a large piece of insultex draped over my head. The specs say this paper thin piece of foam looking material has a clo of 2. That would put it pretty high on the clo charts and above 300 fleece.

Hmmmmm, I'm going to have to ponder this one. I sure don't feel as warm as I would with a 300 fleece blanket draped over me and this insultex stuff is sandwiched between two layers of remay type fabric....which should make it a little bit warmer yet.

I would agree with Matt in that if my head, hands and feet are covered well and pretty warm I can go a lot colder or with less insulation on my arms, legs and torso. But I am really tall and the extremities are even moreso.

I know that Andrew Skurka really liked using an Apex insulation quilt over his Alaska trip and did not notice much if any loft loss over the course of it.

curious. a question about the numbers and statistics that say people lose the majority of heat through their head....

is that heat loss through your skin (same as the rest of your body) or do they calculate the percentage of heat that escapes through the big holes in your body in the head (mouth, nose, ears, eyes). i would think that those gateways into the body's interior would EASILY be the sources of the greatest heat loss.

if that were the case, then the priority of covering one's body with insulation would have to change due to the inability to cover those holes (or the importance of gear like a hat that covers the ears or a balaclava would increase). i can see a down turban in the future!

Your 10 -12% nose and mouth heat loss is covered under the category of respiration heat loss and is a separate category from the body surface area dry heat losses.

The “United States Naval Flight Surgeon's Manual: Third Edition 1991: Chapter 20: Thermal Stresses and Injuries”. It states, “Vaporization of water removes heat from the skin surface and the moist mucous membranes of the respiratory epithelium. When one gram of water is converted into water vapor, 0.58 kilocalories of heat must be supplied from the surroundings for the conversion to occur. Although the actual amount of heat loss depends on the ambient relative humidity, in Antarctica, where humidity is very low, respiration alone may account for ten percent (375 kcal) of an individual's total daily heat loss. Insensible perspiration, as is shown in a later section, accounts for an additional loss of about 400 kcal.” Note the 10% value for Artic respiration.

Okay.. I am a new member of BPL so take it easy on me but....For a long time I have noticed that breathing through my nose even while hiking has advantages over mouth breathing under extremes of cold and heat.Remember I was born and raised in California so if my theory sounds whacked out it's because I am.. er it is.Here goes:Under cold conditions when the air is also very dry breathing air through the mouth causes stress on the lungs and increased dehydration and cooling of the core.Breathing through the nose under similar cold/dry gives the nasal turbinates time to humidfy and warm the air as it is inhaled and recapture some warmth and humidity on the exhale that would be lost out the mouth otherwise.Similarly in very Hot conditions breathing through the nose cools massive amounts of blood in the nasal passages and therefore the head and brain versus mouth breathing. Also nose breathing in Hot dry conditions reduces dehydration by scavenging moisture from the lungs and using it to humidfy incomming dry air in the nasal passages.If you are still with me.. I have found i use less water when i force myself to nose breathe even if it means moderating my pace to allow for it.While it is not always possible to breathe solely through the nose at higher activity levels (such as Colorado's CDT) I found that i can "train" myself to do so for a significant part of the time while climbing uphill.I believe nose breathing doubles the distance i can hike on a liter of water before reaching the same state of dehdration as mouth breathing.I have no hard science to back up my belief.. but I did stay at a Holiday Inn express once.

Look at the dates. Those charts are nearly 2 and half years old. You'll notice the Patagonia uses Polarguard (PGD) and not primaloft. A lot has changed.

Primaloft recently (within the past year) updated the clo of all their products. Some new manufacturing process is my guess. They actually were rather generous and simply replaced all their old products with the improved products instead of differentiating lines and charging more...

Anyway PL1 used to be rated lower (0.89 if memory serves me). Also remember these are MEASURED clo values. The MB and Patagonia both use sewn through construction which decreases clo. Also manufacturer specs aren't always most accurate, with testing conditions usually being optimized to max out the clo value...

I don't quite understand... if you look at Richard's other chart and the chart on top, it appears that I will be more than warm if I wear the Fugu jacket and nothing else on a 0 degree while sitting still. Something seems odd... Am I misinterpreting something?

I didn't dig up the other graph but I am pretty sure I remember the one you are refering to...

The one at the top of this thread gives Iclo (intrensic clo) for various garments. This is the insulation value nominalized for surface area (a 1"X1" square of the jacket would have the same Iclo but much much smaller clo.

The other graph (if I remember) had clo required vs temperature with MET rate traces. The clo required is the total clo of all clothing. If you had the iclo's of all your garments you would have to multiply each by the %body covered and add them together to get clo.

You would need a fugu bodysuit to stay warm at the temperature and activity level.

Outstanding jacket and good value. It weighs (and packs to) almost nothing and kept me warm on a trip to the Alps with temps in the 20's. Pair this with a lightweight waterproof shell and you probably won't need anything else for most endeavors.

According to pata cs this series of garments uses the same amount of down as the down sweater and hoody. Would the clo be the same give that down densityAlso is a contributor to that overall value or have they compressed it too much?ThxPat

They test the same. The key to maximizing the warmth of small down channel garmets, like these, is to always wear them under a windshirt or hardshell. This will capture still air pockets over the seams for significant additional warmth.

I have an old wild things sweater that I want to replace, that has the 2 layers of 60g primaloft 1 quilted together, and the chart gives it a 1.46 iclo. The Rab Xenon, with one layer of 60g primaloft has an iclo of 1.51, and the Rab generator, with 100g of primaloft 1 has an iclo of 2.27. Shouldnt the wild things be similar to the generator, or higher? Thanks

I have made multiple prior posts explaining that NO synthetic garments that I lab tested, unlike the down garments, were close to their theoretical Iclo specification. I don’t doubt the value of the synthetic insulation’s specified Iclo at the time of manufacture, BUT after being manufactured into a garment and boxed and unboxed during distribution, they test, on average, 51% of their theoretical values. This chart is a portion of one of my many prior posts on this topic from a couple of years ago:

About the same time that I did these tests, BPL was manufacturing synthetic garments for UL backpacking. They were also recommending that synthetic garments and quilts be used during their courses. So, TO BE POLICTIALLY CORRECT, after first posting multiple times that ALL synthetic garments that I tested averaged about ½ of their theoretical Iclo value, I posted all subsequent synthetic garment’s Iclo values based on their theoretical specs. For my personal sustained-wet-weather use, I select garments based on the -51% of Iclo spec. lab test results. I try to not dissuade others from making their decisions based on the manufacturer’s specifications if they choose to do so.

I am still trying to figure out how it is that much warmer than my Montbell Alpine jacket. The Fugu is a sewn through construction with less loft and down while the Alpine is box baffled and very puffy. Is it just the metalized inner? Where can I get a jacket just made out of that stuff?

@ Brett - the Fugu has a reflective barrier (think NeoAir with down fill) and an Epic-like fabric which both aid in mitigation of heat loss via radiation and convection respectively. I know of no other down garment that compares. Especially when combined with a well-designed down hood, I still consider it king of lightweight the down-heap. It is hands down the warmest jacket that I own and I only bring it out for sustained winter weather conditions.